Word History: In a Latin work dating from 1620, the English philosopher and essayist Francis Bacon used the phrase instantia crucis, “crossroads instance,” to refer to something in an experiment that proves one of two hypotheses and disproves the other. The word crucis in Bacon's phrase is the genitive form of the Latin word crux. Crux originally meant “cross” but had also developed the meaning “a guidepost that gives directions at a place where one road becomes two” and hence was suitable for Bacon's metaphor. Both Robert Boyle, often called the father of modern chemistry, and Isaac Newton used a similar Latin phrase, experimentum crucis, for an experiment that determines which of two hypotheses is valid. When English equivalents for these phrases were created in the 19th century, they became crucial instance and crucial experiment. Through the influence of these phrases, the adjective crucial, which before this time had meant simply “cross-shaped,” acquired the sense “vital to the determination of an outcome.”

(slang, chiefly Jamaica) Term of approval, particularly when applied to reggaemusic.

Delbert Wilkins is the most crucial pirate radio DJ in Brixton.

Origin

1706, from Frenchcrucial, a medical term for ligaments of the knee (which cross each other), from Latin crux, crucis (“cross”) (English crux), from the Proto-Indo-European*(s)ker- (“to turn, to bend”).

The meaning “decisive, critical” is extended from a logical term, Instantias Crucis, adopted by Francis Bacon in his influential Novum Organum (1620); the notion is of cross fingerboard signposts at forking roads, thus a requirement to choose. Specific quote is:

Sentence Examples

Thirty days isn't long enough for you to complete this first step, and it's crucial you do it right.

They were silent, aware this would be one of the most crucial battles they'd encountered in ages.

The crucial example of this is what Richard Strauss has ingeniously called the "al fresco" treatment of instruments in large orchestral masses (Berlioz-Strauss, Instrumentationslehre, edition Peters)..

None of the people who did crucial experiments on spontaneous generation disproved abiogenesis.

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A person influenced by circumstances can become viciously envious or affectionately kind. Our company and our surroundings have a crucial effect on our consciousness. How important it is to be an instrument to bring out the inherent good of each other rather than the worst. Radhanath Swami